Semiconductor manufacturers are constantly striving to keep up with the increasing speed and number of signals coupled between microcircuits. For example, a microcircuit, such as a microprocessor, can contain billions of transistors with clock speeds greater than three gigahertz. Typically, the signals are routed between microcircuits using metal tracing or metallization systems that can include a plurality of solder balls, wire bonds, bonding pads and the like. The focus of semiconductor manufacturers has been to decrease gate delays within the microcircuits. As a result, the gate delays are now generally less than the delays contributed by the metallization system including the structures for coupling signals between the microcircuits. Thus, because of an increasing demand for smaller and faster microcircuits, there is a need to improve the structures utilized for signal coupling.
A component can include a microcircuit contained within an individual package. When mounted on a printed circuit board (PCB), the component generally provides poor utilization of space, because the microcircuits are generally smaller than the packages that contain them. Further, signal delays have occurred due to the relatively large space between the individual microcircuits contained within the package, so multi-chip module (MCM) and/or system in a package (SIP) designs are used to reduce the required space and the signal delays because the microcircuits are not contained within individual packages. For example, FIG. 1 is an enlarged top-view of a portion of a conventional device 10, or multi-chip module, illustrating a substrate 2 having a surface 25, which can harbor a plurality of microcircuits 7. Typically, the MCM or device 10 can comprise a combination of microcircuits of various semiconductor technologies that can be used to optimize the overall performance. The substrate 2 can contain a plurality of conductive layers (not shown) and typical electrical interfaces between the microcircuits and a printed circuit board. Metal connections or wire bonds are normally used to electrically couple a signal or power between the substrate 2 and the plurality of microcircuits 7. For example, a microcircuit 6 can use a wire bond 16 between bonding pads 14 and 15 on the substrate 2 and the microcircuit 6, respectively. Similarly, a microcircuit 8 can be electrically coupled by a wire bond 20 to the connection on a bonding pad 9 on the substrate 2. Hence, any power or signal received or transferred between the microcircuits 6 and 8 is coupled through wire bonds. As the demand for performance continues, the speed and density of the microcircuits will continue to increase, requiring further scaling of devices. Thus, greater demand for electrical coupling between microcircuits is anticipated.
We describe a structure for electrically coupling across a microcircuit or between microcircuits using a charged particle beam. Electrical coupling includes transferring power and/or a data signal on the charged particle beam. The data signal can be coupled by modulating the charged particle beam. Modulation can include pulsing, deflecting or shaping the charged particle beam. The charged particle beam carrying the signal can be deflected or routed to a particular location across or between microcircuits. The structure can be formed on the microcircuit or microcircuits in a final metallization step of the fabrication process.